The invention relates to the alarm system of a depth sounder and more particularly to a circuit for triggering the transmitter and the depth alarm circuit when the flasher arm motor is turned off.
In the heretofore known prior art depth sounders, alarms have been made to warn the user when the water depth is too shallow but this was only possible with the flasher arm rotating. It can also be of great use to boat operators to have some form of alarm to indicate when the boat deviates from some preset depth or depths while at anchor at which time the full capabilities of the depth sounder are not required and when a mode of operation requiring considerably less battery current is advantageous.
With respect to flasher type depth sounders, it is known that they are popular because they display much information in an easily readable form. However, they require a substantial amount of current for the flasher arm motor. This is particular disadvantageous on small sailboats where no means of charging the battery is available, or when a boat is at anchor and the engine and thus the alternator or generator is off. Heretofore, it has not been possible to switch off the flasher arm motor because the magnet was attached to the rotating flasher arm which magnet was used to key the transmitter. Hence, the need for a depth alarm function which can be operative even with the motor off has been a recognized need for boaters.
Prior art references considered with respect to this invention are U.S. Pat. Nos. 3,223,965; 3,733,582; 3,740,705 and 3,747,413.